1. Field of the Invention
This invention relates in general to dry bulk cargo containers, and in particular to a method or apparatus for closing off the rear end of such a container. More specifically, it relates to providing a partially sealing closure for the rear of a container.
2. Background Art
Use of standard-type ISO cargo containers has come into widespread use in the shipping industry in the last thirty to forty years. Dry bulk, flowable cargos make up one class of cargo shipped in these containers. Use of the container to transport a dry bulk, flowable cargo of up to 44,000 pounds avoids the necessity of having to package small amounts, fifty pounds to one ton, of the cargo in separate packaging, and then place them in the container. The dry bulk cargo is generally blown into or deposited in the container by a gravity feed system.
A number of methods exist for enclosing and sealing the cargo in the container for transport. One involves using a large plastic liner in the container to contain and protect the dry bulk, flowable cargo; U.S. Pat. No. 3,868,042 describes one commonly used method and apparatus. The shipping industry also uses bulkheads of various designs and materials to help support liners and retain cargo in a container. U.S. Pat. No. 4,799,607 provides one example of such a bulkhead which has enjoyed widespread acceptance.
A number of shipping applications do not require the use of such liners because of cost or lack of need. In such situations, the dry bulk cargo can simply be placed in the container by appropriate means and shipped. However, one must still close off the rear of the container while the container doors are open to appropriately contain the cargo and seal it in the container until it arrives at its destination. Cargos quite often shipped by such method without a liner include hops, beans or other raw food commodities before processing, as well as recycled plastic, polyethylene or polypropylene in a pelletized or powder form.
In order to appropriately contain the product in the container and prevent it from spilling out of the rear of the container, a bulkhead is placed across the rear or at some position in the container to create the appropriate cargo space between the bulkhead and front wall of the container.
The preferred current method used in the industry involves placing a rectangular sheet of plywood at the rear of the container, which sheet fits generally snugly with respect to the side walls and floor of the container. FIG. 1 depicts such a bulkhead 25 placed at the rear of a container 21. Doors 22, 23 are shown in the open position. Generally, bracing, consisting of 2.times.4's or other type of wooden or metal bars 24, is placed behind the bulkhead 25, if necessary, to secure it and support it in an upright position in the container. However, with this method, gaps tend to exist at the edges of the plywood bulkhead, namely gaps 29 along the edges of the bulkhead 25 which abut the walls, and gap 26 at the bottom of the bulkhead 25. The cargo or product being shipped will often leak out through these gaps. In order to avoid this, after installation of the bulkhead 25 with bracing 24, a worker has to climb over the top of the bulkhead through the gap 19 between the ceiling of the container and the top of the bulkhead. The worker then, once inside the container, has to brush, spray, or by some other means apply an adhesive to the area covered by plastic sheets 199 and 27. After applying the adhesive to these areas, he then has to press on the sheet of plastic 26 as depicted along the floor, and the sheet of plastic 27 as depicted between the bulkhead and wall. These plastic sheets, when properly placed, then create an appropriate seal to prevent loss of product through gaps 28 and 29. However, this method can prove expensive, given the extra work required. Additionally, it can prove a dangerous method in that, while climbing in or out, the worker could accidently fall or trip and perhaps injure himself/herself. Also, these plywood bulkheads are heavy and clumsy, and are expensive to manufacture. Also, they must be re-used a number of times to recoup their full value.
Another problem with the current art bulkhead as depicted in FIGS. 1 and 2 is the fact that, during loading of many dry bulk, flowable cargos, dust generated by the loading process vents through the opening created by the gap 19 between the top of the bulkhead 25 and the ceiling 21 of the container.